The present invention relates to an end curving device for controlling the bending of the curving section of an endoscope with an operating section which is manually operable by the operator.
In an end curve device for an endoscope, one or two pairs of operating wires coupled to the curving section provided at the end of the endoscope are coupled at their opposite ends to the operating section, and the curving section is bent in a desired direction by pulling one of the operating wires while pushing the other.
Available operating wire driving devices can be generally classified into a first group in which the operating wires are wound on a pulley and the pulley is turned by operating an operating lever, and a second group in which the operating wires are driven through a rack-and-pinion mechanism. In the former group, the construction is relatively simple. However, in order to increase the amount of movement of the operating wires per unit angle of rotation of the pulley, it is necessary to increase the diameter of the pulley, and therefore the operating section is necessarily bulky. Furthermore, since the operating wires are wound on a pulley, the operating wires are repeatedly bent and rubbed by the pulley, leading to relatively frequent breakage of the wires. On the other hand, in the latter group in which a rack-and-pinion mechanism is employed, a pair of racks coupled to a pair of operating wires are engaged with a single pinion, and the pinion is operated to drive the operating wires. If the pinion were to be driven directly with the operating lever, then similarly as in the above-described first group, in order to increase the amount of movement of each operating wire per unit angle of rotation, it would be necessary to increase the diameter of the pinion. Furthermore, since the racks extend beyond the pinion, the operating section is larger in size than that of the first group employing a pulley. The speed of the device may be increased by arranging intermediate gears between the pinion and the racks. However, in such a mechanism, the direction of rotation of the pinion is opposite to the directions of movement of the racks. Therefore, the operating wires must be crossed with each other between the operating section and the curving section at the end of the device. However, crossing the operating wires results in excessively large forces being applied to the operating wires. As a result, the operating wires are liable to be fatigued, worn, and broken.